The present invention relates generally to maintaining engine driven generators and more particularly to diagnostics and prognostics of fielded generators via monitoring of the same.
Conventional monitoring and diagnostic systems for generators may be manufacturer and model specific. Employing model specific generator monitoring systems may be cost prohibitive. A more robust or global application which adapts to a given generator would be desirable for the management, operation, and maintenance of a multitude of diverse generator systems.
In certain applications, to include fielded military applications, the effects of generator down time can have far reaching undesirable consequences. Detecting a fault in an engine driven generator, or in the engine of the same, offers some advantages but forecasting faults from continuous monitoring data could provide further advantages and the opportunity for scheduling downtime and reducing the same.
Unscheduled generator down time can have a multitude of negative consequences. Warnings to avoid system failures are desirable. In order to avoid down time, conventional detection devices have been designed that generate feedback regarding an operating engine driven generator. The feedback is then reviewed by an operator to determine the operating conditions of the generator. However, conventional systems that monitor operating engine driven generators typically provide feedback of faults that have already occurred and may have already damaged the engine-generator. As such, though operational feedback is sent to an operator, it is often too late for preventive action to be taken.
Conventional vibration assessment and identification of vibrational faults pose additional challenges. For example, one conventional system provides prognostics of a rotor cage failure in an induction motor using vibration analysis. More particularly, vibration monitoring has been utilized to provide some early misalignment or unbalance-based faults notice. However, when a mechanical resonance occurs, machine vibrations are amplified. Due to this amplification, false positives indicating severe mechanical asymmetry are possible. Vibration signal analysis is also complicated by its short signal length and non-cyclical nature. Instead of vibrations sensors, U.S. Pat. No. 8,405,339 to Zhang et al. teaches generating a current frequency spectrum of stator current using Fast Fourier Transformation and analysis of resulting harmonics to forecast a rotor fault from current sensor data. However, the Fourier Transform also has limitations with respect to vibration signals, which are discussed below.
Other forms of generator monitoring have been explored at some level, each with its own drawbacks. Such drawbacks include, for example, inaccurate vibration assessment, incomplete diagnosis, technically demanding implementation, customization demands, and a lacking in prognostic capability. It would be desirable to obtain a monitoring system with both diagnostics and prognostics that evaluates a multitude of factors, to include vibration, and that produces an accurate assessment of the generator system condition.